1. Field
The present disclosure relates to light emitting devices, and more particularly to electrodes for light emitting diodes.
2. Background
A light emitting diode (LED) is a semiconductor material impregnated, or doped, with impurities. These impurities add “electrons” and “holes” to the semiconductor, which can move in the material relatively freely. Depending on the kind of impurity, a doped region of the semiconductor can have predominantly electrons or holes, and is referred respectively as n-type or p-type semiconductor regions, respectively. In LED applications, the semiconductor includes an n-type semiconductor region, a p-type semiconductor region, and an active region between the n-type semiconductor region and the p-type semiconductor region. When a forward voltage is applied across the p-n junction, electrons and holes are forced into the active region and combine. When electrons combine with holes, they fall to lower energy levels and release energy in the form of light.
During operation, a forward voltage is applied across the p-n junction through a pair of electrodes. The electrodes are formed on the semiconductor material with a p-electrode formed on the p-type semiconductor region and an n-electrode formed on the n-type semiconductor region. Each electrode includes a wire bond pad that allows an external voltage to be applied to the LED.
Generally, when an external voltage source is applied to the LED, the current does not spread uniformly within the semiconductor regions resulting in a phenomenon known as “current crowding.” Current crowding is the non-homogenous distribution of current density through a conductor or semiconductor, especially in the vicinity of the wire bond pads and across the p-n junction.
Current crowding leads to a reduction in the optical and electrical performance of the LED, particularly for conditions of high average current density and for LEDs that are made with larger diameters. Current crowding can also lead to localized overheating and result in the formation of thermal hot spots. Accordingly, there is a need in the art for improvements in LEDs to reduce current crowding by providing a more uniform distribution of current through the semiconductor material when a forward bias is applied across the p-n junction.